1. Field of the Invention
In this specification, description is made on a lighting device in which a light-emitting diode (LED) and an organic electroluminescence element (organic EL element) are used as light sources.
2. Description of the Related Art
A lighting device referred to as LED lighting is lighting equipment in which a light-emitting diode (LED) that is a kind of a semiconductor element is used as a light source. The LED lighting saves power and has a long life; thus, it has been attracting attention as an alternative to a fluorescent lamp.
Further, an organic electroluminescence element (an organic EL element) is known as a light-emitting element using an organic material. The organic EL element is also a kind of a light-emitting diode, and is also referred to as an OLED or an organic LED in some cases. A typical example of a device using an organic EL element is an organic EL display device in which an organic EL element is used in a pixel. Digital cameras and cellular phones in which organic EL display devices are used in their display portions have been commercialized.
Further, obtaining white light by combining an LED and an organic EL element which emit lights with different wavelengths, has been proposed. For example, Patent Document 1 discloses a lighting device in which an inorganic LED and an organic EL element are combined. Patent Documents 2 to 5 each disclose a display device in which an inorganic LED and an organic EL element are combined.